This invention relates generally to semiconductor fabrication and, more particularly, to a method and apparatus for transferring and supporting wafers for batch processing in a furnace.
Heat-related complications can preclude the use of common wafer boats for very high temperature treatment or processing of a batch of wafers in a furnace, e.g., processing at temperatures up to about 1350xc2x0 C. For example, common wafer boats may support wafers only at their edges. With such a support scheme, because the mechanical strength of a wafer can be reduced at very high temperatures, the wafer""s own weight can cause it to plastically deform at very high temperatures.
Other available wafer boat wafer supports are described in U.S. Pat. Nos. 5,865,321 and 5,820,367. U.S. Pat. No. 5,865,321 describes a wafer boat having a wafer support with multiple inwardly extending arms to support the wafer at more inward locations. U.S. Pat. No. 5,820,367 describes a wafer boat that supports a wafer at a central location using the entire circumference of a ring support. The supports in these wafer boats, however, are still not sufficiently supportive to prevent plastic deformation and consequent crystallographic slip of the wafer. In order to prevent slip, wafers should be supported over a substantial portion of their bottom surface areas.
Wafer supports meeting this criteria are known for single wafer systems. For such systems, susceptors supporting wafers over their entire bottom surface area and support rings forming a complete circle to support a wafer at its perimeter are known in the prior art. Special measures, however, are required to place a wafer onto or to separate a wafer from such susceptors.
In particular, with such a single wafer system, when using a robot end effector according to the prior art, access to the wafer is generally provided from the bottom and the susceptor stays in place within a process chamber while wafers are serially loaded and unloaded. Typically, the robot end effector places a wafer on moveable pins at a level above the susceptor, the wafer being spaced sufficiently above the susceptor to allow enough clearance for retracting the robot end effector without the robot end effector touching the wafer or the susceptor. After retraction, the pins move downward to lower the wafer onto the susceptor. To unload the wafer, the reverse of these steps occurs. While suitable for single wafer processing, such a wafer loading and support system is not easily applicable to a batch processing system because, if possible at all, such a system would be unacceptably complicated and cumbersome, since it would require, inter alia, that every processing position be provided with moveable pins and the attendant hardware and control systems to move these pins.
Accordingly, it is an object of the present invention to provide a wafer boat with a wafer support system that, inter alia, provides support for wafers over a substantial portion of their bottom surface areas and that allows for efficient loading and unloading of the wafers for processing in a process chamber.
In accordance with one preferred embodiment of the invention, a method for semiconductor processing is provided. The method includes loading a wafer onto a wafer support in a transfer station, transporting the wafer into a process chamber from the transfer station and subjecting the wafer to a semiconductor fabrication process in the process chamber. During both transporting the wafer into the process chamber and subjecting the wafer to a semiconductor fabrication process, the wafer is seated upon the wafer support.
In accordance with another preferred embodiment, a method for handling a wafer and a wafer support for processing is provided. The method includes placing a wafer on a wafer support, subsequently transporting the wafer while seated upon the wafer support into a wafer boat, and subjecting the wafer to a semiconductor fabrication process while the wafer is seated upon the wafer support in the wafer boat.
In accordance with yet another preferred embodiment, a system for processing a substrate is provided. The system includes a plurality of substrate supports for supporting a plurality of substrates. The substrate supports support an entire perimeter of a substrate and are held in a substrate support holder, from which they can also be removed. A process chamber accommodates the substrate support holder during substrate processing. The system also comprises a substrate loading station that is configured to load a substrate onto a substrate support, where the substrate loading station is separate from the substrate support holder.
In accordance with another preferred embodiment, a semiconductor wafer cassette is provided. The cassette houses a wafer loading station that is configured for loading a wafer onto a wafer support.